Conduction pump for conveying corrosive metals

ABSTRACT

Conduction pump having slight bulk, in which a section of the liquid metal flow subjected to magnetic induction is crossed at the same time by a current, characterized in that the said section of liquid metal flow is limited on two opposite sides by electrodes connected to a current generator circuit, whereas the other sides are made of refractory material. The electrodes are made of a metal of the VIth group of the periodic classification of elements, protected on the corrosive liquid metal side by a boride or an aluminide, or else the electrodes are made of a refractory material soaked with liquid metal.

lJnited States Patent 1 Carbonnel et al.

[ CONDUCTION PUMP FOR CONVEYING CORROSIVE METALS [75] lnventors: Henri Carbonnel, Antony; Robert Borie, Sceaux, both of France [73] Assignee: Groupement Atomique Alsacienne Atlantique, Robinson, France [22] Filed: Mar. 16, 1972 [21] Appl. No.: 235,278

[30] Foreign Application Priority Data Mar. 16, 1971 France 71.09159 Mar. 30, 1971 France 71.11143 [52] U.S. Cl. 417/50 [51] Int. Cl. l-ll02n 4/20 [58] Field of Search 266/38; 310/1 1, 13; 417/50 [56] References Cited UNITED STATES PATENTS 3,260,209 7/1966 Rhudy 417/50 [451 May 7, 1974 3,288,069 11/1966 Michaux ..4l7/50 Primary Examiner'Wil1iam L. Freeh Attorney, Agent, or FirmSughrue, Rothwell, Mion, Zinn & Macpeak Conduction pump having slight bulk, in which a section of the liquid metal flow subjected to magnetic induction is crossed at the same time by a current, characterized in that the said section of liquid metal flow is ABSTRACT limited on two opposite sides by electrodes connected 11 Claims, 5 Drawing Figures P-ATENTEMAY m4 SHEET 2 [IF 3 BACKGROUND OF THE INVENTION l. Field-of the Invention The present invention concerns a conduction pump capable of conveying corrosive metals, such as, for example, aluminum, zinc, cast iron or steel, in the liquid state. i

2. Description of the Prior Art The use of pumps for liquid metals has been developed at the same time as various techniques requiring the flowing of liquid metals, more particularly for foundry work, the metal purifying treatments and, also, as a heat-bearing fluid in nuclear energy. The operation of these pumps generally makes use of the conductive properties of liquid metals and implements an electromagnetic force which sets the liquid metal in motion. Thus, a distinction is made between two types of electromagnetic pumps: conduction pumps and induction pumps.

In the former, the current is made to pass through a transversal's'ection of the ductand the liquid metal flow it contains, when a magnetic field is set up'perpendicular to the direction of the electric current and to the direction of the liquid metal flow, so that there appears, within the liquid metal, a force directed along the third axis of a trihedral whose first two axes are situated respectively in the direction of the field and in the direction of the current. It has not been possible, up until now, to use this type of pump, which is easy to manufacture when the liquid metal duct is itself conductive, with corrosive liquid metals which would corrode usual metal ducts. Theresult is that in the present state of the art, conduction pumps can be'used only for conveying slightly corrosive metals such as, for example, alkaline metals, lead, mercury or magnesium.

For more active metals, circumstances have-led to the forming of the duct for liquid metal with refractory niaterialsfwhich are generally fairly poor electrical conductors. This fact has led to the use of induction pumps. In this second type of pump, suitably placed magneticcircuits induce, in the liquid metal, a sliding magnetic field which draws the molten metal inside the duct in the same way as the conductive cage of an asynchronous motor is driven in a rotating movement, this relating that type of pump to linear motors.

Nevertheless, these induction pumps are generally fairly bulky, because of the necessity of accommodating the magnetic circuits around a pipe made of refractory material, this preventing their use in the numerous applications whereit is desirable to house the pump in a restricted space. Moreover, this type of pump is not self-primed when the metal to be drawn in is below the level of the pump, and, taking into consideration its bulk, it is difficultto submerge it so as to make it easier to prime it. Hence, the advantage of induction pumps is actually fairly limited.

To overcome the various disadvantages of induction pumps, the applicant has sought to produce conduction pumps for corrosive liquid metals in which electrical contact can be .obtained between a circuit element crossed by anintense current and the flow of corrosive I ticularly, they concern the protection of such electrodes against the corrosive metal, the uneven expansion of the electrode and of the refractory material, and

.lastly fluid-tight sealing between the electrode andthe overcome all these difficulties and produce a type of conduction pump giving satisfactory operation and enabling the handling and conveying of corrosive liquid metals, while having a pump with very small dimensions.

SUMMARY OF THE INVENTION The object of the present invention is therefore a conduction pump, having slight bulk, for corrosive liquid metals, in which a section of the active liquid metal flow crossed by an electric current perpendicular to the direction of the said flow is subjected to an electromagnetic force resulting from the action of that current and from a magnetic induction situated perpendicularly to the direction of the electric current and to the direction of the liquid metal flow, characterized in that the section of the liquid metals flow is limited on two opposite sides by electrodes enabling the electric current to pass, and on its other sides by the refractory material protecting the duct, cast or machined when the pump was manufactured.

When the current crossing the section of the liquid metal flow is direct current, the magnetic induction applied to the liquid metal, produced in the main magnetic circuit, must itself by continuous. When, on the contrary, the current crossing the liquid metal is alternating current, it is necessary for the magnetic induction itself to be alternative. It is then an'advantage to produce that alternating current by induction in a conductive loop. In general, a second magnetic circuit, referred to in the following text, as the secondary magnetic circuit, is used.

The main magnetic circuit, and, possibly, the secondary magnetic circuit, each comprise an induction winding. The reluctance of the magnetic circuits is produced sufficiently low, so that it is possible to place these windings at a sufficient distance from the pumping area for them not to be submitted to the direct thermal action of parts brought to a high temperature.

The bulk of the pump is thus reduced round the duct containing the liquid metal.

The conductive loop can, itself, consist of a conventional metal conductor (copper or nickel, for example). On the other hand, the electrode must consist of a metal having a coefficient of thermal expansion as near as possible to that of the refractory material used, so as not to let any gap be formed, by expansion, between the two materials; moreover, it must be possible to weld it to the conductive loop, and more particularly, it must be capable of withstanding the action of all the reactive metals without suffering damage. It can be seen that no material having all these qualities exists. The applicant has therefore been led to find a solution to that complex problem by choosing a metal whose coefficient of expansion is perfectly suitable, and by coating it on each of these surfaces with a substance which enables the joining thereof to its own environing medium.

metal, and to use an electrode consisting of a refractory material impregnated with metal.

Such devices have, in relation to prior art, numerous advantages resulting, more particularly, from the fact that it is possible to immerse them in the liquid metal, so that it is possible to start them up without having to prime them by an outside means. Moreover, the immersion depth required for self-priming is much less than for an induction pump.

Moreover, the cross-section of the pump body is much less bulky, since the windings can be mounted far from the pump body. In the case of pumping, by immersion, of a metal contained in a crucible or in a casting ladle, the volume immersed is therefore much less; there are only smalllosses in capacity of the-useful volume of the crucible or of theladle. Moreover, the windings are arranged above the bath and are easier to protect against any accidental raising of their temperature.

All these advantages add up to confer on this new type of pump a particular aptitude for use inpumping, by immersion of liquid reactive metals.

Moreover, pumps of this type are also capable of compensating a great metallostatic pressure; they can therefore be installed at the base ofa ladle or ofa crucible and act as a regulator for the flow of metal, like a stopper rod in which the movement of the mechanical parts has been replaced by a variation of the induction current.

The invention will be better understood on referring to the examples of embodiments described below by way of illustrations of the invention having no limiting character.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an operating diagrammatic perspective view of an electromagnetic direct current or alternating currentconduction pump of the present invention.

FIGS. 2 and Sam perspective views of two particular structures of the invention, both of the alternating current type.

FIG. 4 is a partial perspective view showing the inserting of aconductive loop in the liquid metal duct.

FIG. 5 is a sectional view of an embodiment having a conductive loop provided with solid electrodes.

DESCRIPTION OF PREFERRED EMBODIMENTS On referring to FIG. 1, it can be seen that an electromagnetic conduction pump comprises, at 1, a duct through which the corrosive liquid metal flows. Elements of the electric circuit through which a high current flows in a direction perpendicular to the liquid metal flow direction represented by the line 4 and 4. of the duct 1, can be seen at 2 and 2'. The eletric circuit is extended through the liquid metal by electrodes 5 and 6 designed to setup the electric contact with the corrosive liquid metal. A winding 7 gives rise, in the section of the liquid metal crossed by the current, to a magnetic induction perpendicular to the current and to the direction 4-4 of the liquid metal flow. It is known that a force perpendicular to the current and to the magnetic induction which therefore tends to set the liquid metal in motion alongits duct in the direction 4-4 is then set up in the conductive medium formed by the liquid metal.

When the winding 7 is crossed by an alternating current, and when this is so with the electric circuit 2-2', the force exerted on the liquid metal does not change directions, and continues to push the metal in the same direction as long as the electric current and the magnetic induction change directions at the same time.

FIGS. 2 and 3 show the operating diagram of two types of configurations used frequently by applicant. The diagram of FIG. 2 corresponds to the configuration where the alternating current which flows through the liquid metal is set up by a secondary winding 8 through which a current inphase with the current flowing through the winding 7 flows. The magnetic circuit 9 is the main magnetic circuit. The magnetic circuit 10, which is the secondary circuit, induces in the loop .11 a current passing through the liquid metal duct 1 .by means of the electrodes 5 and 6. Such a configuration requires two windings and two complete magnetic circuits. It can be'preferable to use a configuration such as that in FIG. 3, in which a single transformer 7 sets up a magnetic induction in the duct 1 on the one hand, and sets up a current which crosses the liquid metal flow by means of the electrodes 5 and 6, in the coil 11, on the other hand. I s

In FIGS. 2 and 3, the loop passes twice through the magnetic field to compensate the armature reaction, this having the effect of increasing very appreciably the air gap and consequently, the reluctance of the magnetic circuit. It many embodiments, the conductive loop passes above or below the main magnetic circuit 9, and the air gap can thus be greatly reduced.

FIG. 4 shows, on a larger scale, a view of the arrangement of a conductive coil in a conduction pump.

Firstly, an element of the main magnetic circuit 9 will be noted; in the air gap 12 of that magnetic circuit, is placed the corrosive liquid metal duct 1. It can be seen that it takes the form of a column having a generally rectangular cross-section. At one of the ends of the electrode 5, the existence of a shoulder 13, which extends vertically right along the conductive loop, will be observed. The conductive loop can be a nickel or copper bar. In the latter case, the copper bar must be protected from oxidation by a non-oxidizable covering, such as an inconel tube, for example.

FIG. 5 makes it easier to understand the detail of the structure of the solid loop 11. The shoulder 13, as well as the three other shoulders, 14, 15 and 16, is again shown. In the example of the embodiment, the loop connecting the electrodes consists of a copper bar 19. Initially, the bar chosen is cylindrical; it is inserted in an inconel tube 20. After drawing to produce a flat conductor, the assembly is rolled. By this method, it is possible also to obtain a copper conductor separated from the inconel by an oxide layer, such as, for example, alumina or magnesium oxide, this making differential expansions between copper and inconel easier.

The electrodes 5 and 6 consist of a metal having very substantially the same coefficient of expansion as the refractory material with which they are coated. The applicant has chosen to produce electrodes made of molybdenum. He has also manufactured such electrodes with other metals such as, for example, molybdenumtungsten alloy. To effect the weld with the copper loop, it is' necessary to deposit previously, on the section 17 of the electrode, a layer of nickel. The portion 18 of the electrode 6, which remains in Contact with the corrosive liquid metals, must be coated with a layer ensuring excellent electrical conductivity and it must be possible to wet it easily with the liquid metal. It must, moreover, have excellent adherence tothe electrode and great insensitivity to thecorrosive'liquid'metals used. Long research'has enabled the applicant to determine that conductive ceramic materials compounds such as diborides of molybdenum, titanium, zirconium and tungsten, as well as titanium aluminide, give satisfactory results. In the example of an embodiment, the coating has been formed by molybdenum diboride. The rest of the electrode must be coated with a layer isolating it from air, and providing good contact with the refractory material.

The applicant has used, for that purpose, nickel, titanium, aluminide, and, lastly, commercial products found on the French market, such as Revetox made by the French firm of CERAVER.

The coatings on the faces 17 and 18 of the-electrode can be made, for example, either in a gaseous medium or in a fluidized gaseous plasma support. The parts thus produced are then coated with a mass of refractory material 21 which has'been produced by way of an experiment with various ceramic materials such a alumina, zirconium, magnesia, titanates of aluminum and magnesium, and various zirconates and aluminates.

A second example of an embodiment concerns the pump in which the electrode can be made, as in the preceding case, of molybdenum or protected tungsten, but it can, to great advantage, be produced by means of a porous refractory substance or of a porous refractory sintered structure.

In order to providesatisfactory conductivity through that electrode, as well as a perfect possibility of wetting the latter with the liquid metal, the applicant has contrived to impregnate the electrode prior to its insertion in the apparatus by means of one of the metals to be made to flow in the pump, or at least of a metal which will subsequently be dissolved easily in the molten metal. The applicant has successfully attempted to impregnate with aluminum on condition that the latter be the metal to be conveyed subsequently, and also, to impregnate with tin and copper, which can easily be mixed with metals to be conveyed in the liquid state.

The method used for impregnating such an electrode is as follows: the porous product is put in a container where there is a vacuum and it is wetted at a high temperature with liquid metal. It is important to use a very high temperature just below the evaporating temperature of the liquid metal so as to use it in the most fluid state possible. Then the electrode is impregnated under pressure with the same liquid metal.

To mold the circuit of the coil, a pipe having a slight thickness, made of the same metal as that which is to be conveyed by the pump the first time, can be used. The pipe is made to the outer dimensions of the coil. It is embedded in the refractory material, melted at the first operation of the pump, and drawn in by draining of the coil when the latter is withdrawn from the liquid metal bath.

Although the devices which have just been described appear to be of the greatest advantage for implementing the invention, it will be understood that various modifications can be made thereto without going beyond the scope of the invention, it being possible to replace certain elements by others capable of fullfilling the same technical function therein.

What is claimed is:

1. In a conduction pump having slight bulk for corrosive liquid metals, in which a section of the liquid metal flow, limited on two opposite sides by electrodes, and on its other sides by a refractory ceramic material crossed by an electric current perpendicular to the direction of the said flow and subjected to an electromagnetic'force resulting from the action of that current and from a magnetic induction perpendicular to the direction of the electric current and to the direction of the liquid metal flow,.the improvement wherein at least the portions of the surfaces of the electrodes placed in direct contact with the corrosive liquid metal are coated with a conductive ceramic material which is highly resistant to the attack of corrosive metals.

2. The conduction pump according to claim 1, wherein the material used for forming electrodes is an alloy of metals of group VI in the periodic classification of elements, coated by said conductive ceramic material on the surface in contact with the corrosive liquid metal.

3. The conduction pump according to claim 1, wherein each electrode is coated with a layer of diboride of a metal of group VI in the periodic classification of elements, on the side where it comes into contact with the corrosive liquid metal.

4. The conduction pump according to claim 1, wherein each electrode is coated with a layer of aluminide ofa metal of group VI in the periodic classification of elements, on the side where it comes into contact with the corrosive liquid metal.

5. The conduction pump according to claim 1, wherein each electrode is coated on several sides with an aluminide of a metal of group VI of metals in the periodic classification of elements.

6. The conduction pump according to claim 1, wherein the magnetic induction to which the section of the liquid metal flow is subjected is produced in a main magnetic circuit containing a main winding through which an alternating current flows and in which the electric current crossing said section of the active liquid metal flow is induced by means ofa secondary magnetic circuit in a conductive loop electrically connected to the electrodes, and wherein the induction winding of the main circuit and the induction winding of the secondary circuit are both arranged outside the liquid metal, when the pump is in service, at one end of their respective circuits and separated from the conduction loop and from the electrodes of the pump by a thermal screen constituted by thick layer of ceramic substance.

7. The conduction pump according to claim 6, wherein the conduction loop is formed by means of a bar having a rectangular cross-section, made of highly conductive metal, covered on four surfaces with a casing by means of a metallic layer, protecting against oxidation, made of inconel, drawn and rolled at the same time as the said conductor and wherein said coil is welded on its last two faces onto the electrodes through a layer of nickel.

8. In a conduction pump having slight bulk for corrosive liquid metals, in which a section of the liquid metal flow, limited on two opposite sides by electrodes, and on its other sides by a refractory ceramic material crossed by an electric current perpendicular to the direction of the said flow and subjected to an electromagnetic force resulting from the action of that current and from a magnetic induction perpendicular to the direction of the electric current and to the direction of the liquid metal flow, the improvement wherein at least the portions of the surfaces of the electrodes placed in direct contact with the corrosive liquid metal are coated with a porous ceramic material which is impregnated with either the corrosive liquid metal itself or a metal which will dissolve easily in the corrosive liquid metal.

9. The conduction pump according to claim 8, wherein the porous ceramic product constituting the trodes are made is a refractory zirconate. 

2. The conduction pump according to claim 1, wherein the material used for forming electrodes is an alloy of metals of group VI in the periodic classification of elements, coated by said conductive ceramic material on the surface in contact with the corrosive liquid metal.
 3. The conduction pump according to claim 1, wherein each electrode is coated with a layer of diboride of a metal of group VI in the periodic classification of elements, on the side where it comes into contact with the corrosive liquid metal.
 4. The conduction pump according to claim 1, wherein each electrode is coated with a layer of aluminide of a metal of group VI in the periodic classification of elements, on the side where it comes into contact with the corrosive liquid metal.
 5. The conduction pump according to claim 1, wherein each electrode is coated on several sides with an aluminide of a metal of group VI of metals in the periodic classification of elements.
 6. The conduction pump according to claim 1, wherein the magnetic induction to which the section of the liquid metal flow is subjected is produced in a main magnetic circuit containing a main winding through which an alternating current flows and in which the electric current crossing said section of the active liquid metal flow is induced by means of a secondary magnetic circuit in a conductive loop electrically connected to the electrodes, and wherein the induction winding of the main circuit and the induction winding of the secondary circuit are both arranged outside the liquid metal, when the pump is in service, at one end of their respective circuits and separated from the conduction loop and from the electrodes of the pump by a thermal screen constituted by thick layer of ceramic substance.
 7. The conduction pump according to claim 6, wherein the conduction loop is formed by means of a bar having a rectangular cross-section, made of highly conductive metal, covered on four surfaces with a casing by means of a metallic layer, protecting against oxidation, made of inconel, drawn and rolled at the same time as the said conductor and wherein said coil is welded on its last two faces onto the electrodes through a layer of nickel.
 8. In a conduction pump having slight bulk for corrosive liquid metals, in which a section of the liquid metal flow, limited on two opposite sides by electrodes, and on its other sides by a refractory ceramic material crossed by an electric current perpendicular to the direction of the said flow and subjected to an electromagnetic force resulting from the action of that current and from a magnetic induction perpendicular to the direction of the electric current and to the direction of the liquid metal flow, the improvement wherein at least the portions of the surfaces of the electrodes placed in direct contact with the corrosive liquid metal are coated with a porous ceramic material which is impregnated with either the corrosive liquid metal itself or a metal which will dissolve easily in the corrosive liquid metal.
 9. The conduction pump according to claim 8, wherein the porous ceramic product constituting the electrodes is a refractory oxide material sintered in a porous form.
 10. The conduction pump according to claim 8, wherein the porous ceramic product of which the electrodes are made is a refractory titanate.
 11. The conduction pump according to claim 8, wherein the porous ceramic product of which the electrodes are made is a refractory zirconate. 